Esters of alpha-acyloxy acrylic acids



Patented Mar. 7, 1950 UNITED STATES PATENT. OFFICE ESTERS OF oc-ACYLOXY ACRYLIC ACIDS William 0. Kenyon and Cornelius (J. Unruh, Rochester, N. Y., assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Application September 19, 1947, Serial No. 775,144

' '1 Claims. (01. 260-484) This invention relates to a process for preparing esters of a-acyloxyacrylic acids.

Spence and Degering in U. S. Patent 2,407,302,

dated September 10, 1946, have shown that esters of e-acyloxyacrylic acids may be prepared by reacting a ketone with a ketoester, such as ethyl pyruvate. However, a reaction mixture which is difficult to separate into its component parts acids in increased yields and in condition suitable for polymerizing.

A further object of this invention is to provide valuable new intermediates which may be used in the preparation of esters of m-acyloxyacrylic acids. Other objects will hereinafter become apparent from a consideration of the following description.

According to the process of the present invention, we react an a-acyloxyacrylonitrile with an anhydrous hydrogen halide and an alcohol, producing the hydrohalide of an a-acyloxy-B-halopropionoimino ether, which can be hydrolyzed to the corresponding p-halo -ester by addition of water. This ester is then dehydrohalogenated to Z-ethylhexyl (i. e., an alkyl group having the the desired a-acyloxyacrylic Tester by treatment with an organic tertiary amine.

The e-acyloxyacrylonitrilesi which we may advanta'geously use may ber e'presented by the formula:

wherein R represents an alkyl group, such as methyl, ethyl, propyl, isopropyl (i. e., an alkyl group having the formula CnHLn-j-i where n is a positive integer from 1 to 3)." Typical are a-acetoxyacrylonitrile,-- I rat-blitYlOXYQOIYlODitIiIB, and a-isobutyroxyacrylonitrile.

The alcohols which we may, use may be repre-,

sented by the formula: I

wherein R1 representsa member selected from the group consisting of an alkyl group, such as methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, secondary and tertiary butyl, amyl, isoamyl, n -hexyl, isohexyl, z-ethylbutyl, n-heptyl, n-octyl,

formula CnH2n+1 where n is a positive integer from 1 to 8), and an aralkyl group, such as benzyl, c-phenylethyl, ,B-phenylpropyl, B-phenylbutyl (i. e., an aralkyl group containing a mononuclear aryl group of the benzene series, having 'I to 10 carbon atoms). Typical are methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, secondary and tertiary butyl alcohols, n-amyl alcohol, isoamyl alcohol, n-hexyl alcohol, isohexyl alcohol, 2- ethylbutyl alcohol, n-heptyl alcohol, n-octyl alcohol, 2-ethylhexyl alcohol, benzyl alcohol,

fl-phenylethyl alcohol, p-phenylpropyl alcohol,

and p-phenylbutyl alcohol, etc.

The hydrogen halides which we can use can be represented by the formula:

:where X is a halogen atom, such as chlorine,

bromine, and fluorine. These hydrogen halides must all be used in substantially anhydrous form, preferably in the form of a gas.

The mechanism of the reaction may be represented as follows:

where R, R1, and X have the above-designated definitions.

Alternatively, in lieu of starting with an acyloxyacrylonitrile, it is possible to start with a nitrile represented by the formula:

xom-cH-oEN where R and X have the definition set forth" above. The nitriles represented by the above formula can be prepared, by the addition of one vmol. of hydrogen halide to one mol. of an e-acyloxyacrylonitrile according to the equation:

CHI.-=CO'=N Bx xom-on-ozn -CR C-R II I 0 The a-acyloxy-fi-halopropiononitrile can then be reacted with additional anhydrous hydrogen halide and an alcohol without separation from the crude reaction mixture.

:Anotheralternative procedure is to react the a-acyloxyacrylonitrile' or a-acyloxy-p-halopropionitrile with anhydrous I-IX to produce the The reactants aregenerally employed in substantially stoichemetric quantities. ,Howeveiyit may be advantageous to use an excess of nitrile, since the nitriles are excellent solvents for the reaction and tend to minimize the effects of the corrosive hydrogen halide gases. Solvents may likewise be employed to advantage in our process. Representative solvents are the halogenated hydrocarbons boiling above 10 C., e. g., ethylene dichloride, chloroform, carbon tetrachloride, etc., aromatic hydrocarbons such as benzene, toluene, xylene, etc., diethyl ether, diisopropyl ether, the cyclic ethers such as dioxane, etc.

Due to the exothermic nature of" the reaction of the hydrogen halide -with the-"nitrile, it is advantageous to employ artificial cooling means while the hydrogen halide gas is being passed into the reaction vessel. Durin the addition of the hydrogen halide the temperature of the reaction vessel is maintained approximately .at -20 C. to avoid decomposition of the unstable imino-ether hydrohalide. Solvents provide for more efficient temperature control, and, therefore, it is generally preferred to use asolvent Whenever possible. The solvent need not be added all at once, but can be gradually added The tertiary amines "-Which'we can advanta geously use are the aliphatic tertiary amines; each astrimethyl amine, triethyl amine, tripropy-lamine, tributyl amine; the aromatic amines, such as N,N-dimethyl aniline,- N,N-die thyl aniline; and heterocyclic amines, such as pyridine, quinoline, etc. Other organic tertiary amines can be likewise used Without difficulty.

The following examples will serve to characterize our invention further:

184 grams of absolute ethyl alcohol are dissolved in 2 liters of isopropyl ether, and the vessel'containing the solution immersed in an ice bath. Anhydrous hydrogen chloride is then bubbled through the solution until thevessel has gained 407 grams in weight. Thereupon, 444 grams .of ueacetoxyacrylonitrile are added, and

'4 the temperature of the contents' of the; vessel allowed to rise to that of -the room.- When the temperature of the mixture rises above that of the room, the contents are again cooled by immersion in the-icebath. After standing at room temperature for four hours a copious, crystalline precipitate of a-acet0xy-/3-chloropropionoimino ethyl ether hydrochloride has formed, and is then filtered off and dried at room temperature. After drying, 400 grams of the ether:

oionr-on-tt-oolni-noi ethyl-c-acetoxy-B-chloropropionate, boiling at' 9.7..5to 98;0 C. at5 mm. and having theiformula:

are obtained. I This ester is then dissolved in 200'grams of quinoline and 1000 cc. of dry, thiophone-free benzene. The resulting solution is then stirred under reflux for 20 hours, and the benzene solution concentrated by'boiling. After concentration of the residual oil under vacuum,

a 94%,yield (1&9 grams) of ethyl-a-acetoxy-' acrylate, boiling at 84-.85 C. at 15 mm., is obtained. The product is then purified by dissolving ,in .thiophenefreelbenzene and washing with ice-cold 2%. sulfuric acid, followed by Wash ings with cold water and cold2% sodium carbonate solution. The benzene layer .is thenfdried, and the, benzenedayer concentrated. The residual'oil is then fractionated under vacuum.

Upon polymerization of the monomer with benzoyl' peroxide, a hard, clear and colorless toughpolymerisobtained.

Found Analysis 5 Caleulated Monomer l Polymer When 435 grams of, anhydrous benzyl alcohol replace 184 grams of absolute ethyl alcohol in the above example, benzyl-a-acetoxyacrylate having the formula-z In the manner described above in Example- 1,

184 grams of absolute'ethyl alcohol are dissolved in 2 liters of isopropyl ether, and the vessel containing the solution immersed in an ice-bath. Anhydrous hydrogen chloride is then passed into the solution until the vessel has gained 407 grams in weight. Thereupon, 556 grams of a-butyroxyacrylonitrile are added, and the temperature of the contents of the vessel allowed to come to room temperature. While maintaining the temperature of the solution at 20-25 C., the solution is allowed to stand for 44% hours, during which time a voluminous precipitate of a-butyr oxy-fl-chloropropionoimino ethyl ether hydrochloride forms. After separation of the precipitate from the solution, 800 grams of distilled water are added, and the solution warmed gently on a water bath. After a few minutes a colorless oil separates out, which is well washed with water, and then dried. Distillation or" the oil in a rectifying column gives ethyl-a-butyroxy-fichloropropionate boiling at 113 to 114 C. at '7 mm., and having the formula:

This ester is then dissolved in 200 grams of quinoline and 1000 cc. of thiophene-free benzene. The solution is then stirred under reflux for 20 hours, and the benzene solution concentrated by boiling. After concentration of the residual oil under vacuum, ethyl-a-butyroxyacrylate is obtained, boiling at 95-96 C. at 11 mm. The ester can be further purified by dissolving in thinphene-free benzene, washing with water and cold 2% sulfuric acid, followed by a washing. with cold 2% sodium carbonate solution. The benzene can then be evaporated off, and the ester fractionally distilled.

Butyl-a-propionoxyacrylate can be similarly prepared by substituting butyl alcohol for the ethyl alcohol and u-propionoxyacrylonitrile used in the above example. Its formula can be represented as:

Other esters of a-acyloxyacrylic acids can be prepared in accordance with the above examples. The tertiary amines employed can be recovered and used over again, if so desired. The process of the present invention is particularly advantageous in that esters in exceptionally pure form may be prepared in excellent yields, and the esters so prepared can either be homopolymerized or copolymerized with other polymerizable compounds without difficulty.

We claim:

1. A process for preparing an ester of an aacyloxyacrylic acid which comprises reacting a nitrile having the formula:

wherein R is an alkyl group having 1 to 3 carbon atoms with an alcohol having the formula:

R1--OH 0 wherein R, R1, and X have the above designated definitions, thereafter adding water to produce an ester having the formula:

adding a tertiary amine and refluxing the solution to produce an ester having the formula:

wherein R and R1 have the above-designated definitions, and separating the a-acyloxyacrylic acid ester from the reaction mixture.

2. A process for preparing ethyl-a-acetoxyacrylate which comprises reacting u-acetoxyacrylonitrile with ethyl alcohol in the presence of anhydrous hydrogen chloride to produce aacetoxy-p-chloropropionoimino ethyl ether hydrochloride, adding water to hydrolyze the aacetoxy-e-chloropropionoimino ethyl ether hydrochloride to ethyl-oc-ELCGtOXY-fi-ChIOIOPI'OPlO- nate, adding an organic tertiary amine and refiuxing the mixture to produce ethylm-acetoxyacrylate represented by the formula: 1 i

and separating the ethyl-a-acetoxyacrylate from the reaction mixture.

3. A process for preparing ethyl-a-acetoxyacrylate which comprises reacting a-acetoxyacrylonitrile with ethyl alcohol in the presence of anhydrous hydrogen chloride to produce oracetoxy-p-chloropropionoimino ethyl ether hydrochloride, adding water to hydrolyze the oracetoxy-p-chloropropionoimino ethyl ether hydrochloride to ethyl-a-acetoxy-p-chloropropionate, adding quinoline and refluxing the mixture to produce ethyl-u-acetoxyacrylate represented by the formula:

and separating the ethyl-a-acetoxyacrylate from the reaction mixture.

4. A process for preparing an c-acyloxy-phalopropionate. which comprise'gtreacting a .Sni; trile having the formula:

CHFC;CTEN -0 11 H wherein R represents an alkyl group having l to 3 carbon atoms, with an alcohol having the formula:

wherein R is a: member selected from the group consisting of an alkyl group having the formula C1LH21L+1 wherein n is a positive integer of from 1 to 8, and a mononuclear aralkyl group of the benzene series having from 7 to 10 carbon atoms, in the presence of an anhydrous hydrogen halide having the formula: HX wherein X'is a halogen atom selected from the group consisting of chlorine, bromine, and fluorine atoms, hydrolyzing the a-acyloxy-fi-halopropionoimino alkyl ether hydrohalide so formed by the addition of water,

and separating the precipitated a-acyloxy-phalopropionic acid ester from the aqueous solution.

5. A process for preparing ethyl-a-butyroxyacrylate which comprises reacting a=butyroxy acrylonitril'e with ethyl alcohol in the presence of anhydrous hydrogen chloride to produce ozbutyroxy-B-chloropropionoimino ethyl ether hydrochloride, adding water to hydrolyze the ocbutyroxya-chloropropionoimino ethyl ether hydrochloride to GthYI-oc-blltYIOXY-fi-ChlOIOplODiO- hate, adding an organic tertiary amine and refluxing the mixture to produce ethyl- -butyroxyacrylate represented by the formula:

and separating the ethyl-1x-butyroxyacrylateirom the reaction mixture.

to. produce. .ethyl-a-butyroxyacrylate represented.

by the formula:

and separating the ethyl-a-butyroxyacrylate from g the reaction mixture.

7. A process for preparing ethyl-m-acetoxy /3 chloropropionate which comprises reacting aacetoxyacrylonitrile with ethyl alcohol in the presence of anhydrous hydrogen chloride, hydrolyzing the a-acetoXy-B-chloropropionoimino ethyl ether hydrochloride, so formed, by the addition of water, and separating the precipitated ethyle-acetoxy-fi-chloropropionate from the aqueous i solution.

WILLIAM o. KENYON. CORNELIUS c. UNRUH.

REFERENCES CITED The following references are of record in the file of this patent:

Karrer', Organic Chemistry 2nd edition, 1946, page 211.

Certificate of Correction Patent N 0. 2,499,392 March 7, 1950 WILLIAM O. KENYON ET AL. It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 1, lines 6 and 10, for ketone read Icetene; column 2, line 45, for that portion of the formula reading R-C=O read R%O; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 4th day of July, A. D. 1950.

THOMAS F. MURPHY,

Assistant Commissioner of Patents. 

1. A PROCESS FOR PREPARING AN ESTER OF AN AACYLOXYACRYLIC ACID WHICH COMPRISES REACTING A NITRILE HAVING THE FORMULA: 